合成与实际污水中聚磷菌厌氧代谢研究

以实际生活污水为进水，在实验室对连续流A／O除磷系统进行了聚磷菌的驯化与培养，当系统对磷的去除率稳定在95％以上时利用烧杯批式试验考察了合成污水与实际污水中聚磷菌的厌氧代谢过程，并基于生物除磷的Mumleitner代谢模型，根据试验数据推求了表征聚磷菌厌氧代谢特性的化学计量参数及反应速率。结果表明，合成污水与实际污水中聚磷菌厌氧代谢过程生成的聚β羟基链烷酸的成分及反应速率存在显著差异，研究结果对采用活性污泥数学模型准确模拟实际污水中的生物除磷过程具有一定的参考价值。     

丙酸/乙酸比值对反硝化除磷的影响

分别以丙酸、丙酸/乙酸(浓度比值为0.5、2)、乙酸为碳源,在SBR中采用厌氧/缺氧方式驯化富集反硝化聚磷菌(DPB),研究了丙酸/乙酸比值对反硝化除磷系统中有机物的降解、PO3-4-P的释放与吸收、NO-x-N浓度、PHB和糖原含量以及污泥中磷含量的影响.结果表明,随着丙酸/乙酸比值的提高,厌氧释磷量减少,厌氧末期的PHB含量降低,缺氧段聚磷菌的合成和代谢能力减弱,最终导致对PO3-4-P的去除率降低.因此,乙酸含量高的碳源更利于反硝化除磷的进行.     

不同城市污水处理厂反硝化除磷性能的比较研究

对采用不同工艺的3个城市污水处理厂的活性污泥进行了厌氧释磷、好氧聚磷及反硝化聚磷试验研究,以确定其反硝化除磷能力及差异性。3个污水处理厂采用的工艺分别为内设厌氧段的Carrousel氧化沟(A/O)、外设厌氧池的Carrousel氧化沟(A/C)和具有独立厌氧、缺氧及曝气池的A2/O工艺。结果表明,A/O工艺中活性污泥的释磷能力相对较强,A/C与A2/O工艺中活性污泥的释磷能力相当;A/C工艺中活性污泥的好氧聚磷和反硝化聚磷能力均优于其他两种工艺,好氧聚磷量和反硝化聚磷量分别为15.39和8.09 mgP/gVSS,活性污泥中存在数量可观的反硝化聚磷菌(DPB),反硝化聚磷菌与好氧聚磷菌的比例(DPB/PAO)为57.7%;A/O和A2/O工艺的活性污泥中同样存在DPB,但DPB/PAO值较低,分别为32%和27%。     

SBAR好氧颗粒污泥PHB与除磷的关系研究

实验模拟城市生活污水作为原水,为研究温度控制在10+1℃左右时,SBAR好氧颗粒污泥中DPB反硝化除磷,对好氧颗粒污泥细胞内PHB的作用规律进行了分析,并对其进行了染色分析。结果表明:乙酸钠作为碳源时,反硝化聚磷菌利用COD合成了大量PHB,同时释放大量聚磷酸盐,并得出它们之间的关系曲线,缺氧段吸磷效果明显,除磷效果较好。     

湖滨湿地基质—水界面磷释放特性研究

以湖滨湿地基质和原位上覆水为材料，分别模拟了在好氧及厌氧、不同pH值及不同上覆水初始磷浓度条件下基质中磷的释放特性和规律。研究结果表明，与好氧条件相比，厌氧状态大大促进了基质中磷的释放，且碱性条件下的释放最明显，而中性条件下的释放则较弱，释放强度随pH值的升高而升高。好氧条件下，基质向水体中释磷很少，有时甚至从水体中吸磷。当上覆水的初始磷浓度较低时，基质先向上覆水释磷，而后吸附直至达到平衡；随着上覆水初始磷浓度的升高，当基质中的磷含量低于上覆水中的磷浓度时，则从水体吸磷直至达到平衡。将不同环境因子相比较，上覆水为碱性条件（pH=11．3）时基质的释磷量最大，厌氧条件次之，上覆水的pH值增加和氧化还原电位降低是湿地基质释磷的主要机制。     

序批式生物膜反应器的生物膜特性研究

通过扫描电镜对具有除磷功能的序批式生物膜反应器中生物膜的形态结构进行了观察，并考察了容积负荷、曝气量和厌氧循环水量对生物膜量的影响。结果发现，生物膜主要由微生物及其胞外多聚物组成，大量的微生物及其胞外多聚物相互连结，形成稳定的缠结结构。平均每片填料上附着的生物膜质量为4．088g，挥发性生物膜质量与生物膜干质量的比值为0．861，表明活性生物量较高。填料上的生物膜量主要受曝气量和厌氧循环水量的影响，而容积负荷对填料上的生物膜量基本没有影响。     

A2N反硝化脱氮除磷工艺厌氧释磷的影响因素

利用富含反硝化聚磷菌的厌氧污泥进行静态释磷试验,探讨了A2N双污泥工艺中反硝化聚磷菌厌氧释磷的影响因素.试验结果表明:适当提高温度有助于厌氧释磷;增加污泥浓度(MLSS)和碳源浓度,可以有效强化厌氧释磷效果;碳源类型与厌氧释磷密切相关,投加醋酸钠的效果最佳.     

亚硝酸盐对聚磷菌厌氧代谢的影响

以2种强化生物除磷(EBPR)系统中的活性污泥为研究对象,考察亚硝酸盐对聚磷菌厌氧代谢的影响,结果表明：不同EBPR系统中的聚磷菌对于亚硝酸盐的耐受能力不同。人工配水富集聚磷菌的活性污泥,当亚硝态氮浓度超过10 mg/L时,聚磷菌吸收VFA受到抑制, PHA的合成减少,磷酸盐的释放增加;处理生活污水的SBR短程脱氮除磷活性污泥,亚硝酸盐的浓度高达30 mg/L时,未对聚磷菌的厌氧代谢造成抑制,但引起异养反硝化菌与聚磷菌竞争VFA,导致PHA合成量和释磷量的减少。富集聚磷菌的活性污泥投加亚硝酸盐后P/VFA     

湖滨湿地基质-水界面磷释放特性研究

以湖滨湿地基质和原位上覆水为材料,分别模拟了在好氧及厌氧、不同pH值及不同上覆水初始磷浓度条件下基质中磷的释放特性和规律.研究结果表明,与好氧条件相比,厌氧状态大大促进了基质中磷的释放,且碱性条件下的释放最明显,而中性条件下的释放则较弱,释放强度随pH值的升高而升高.好氧条件下,基质向水体中释磷很少,有时甚至从水体中吸磷.当上覆水的初始磷浓度较低时,基质先向上覆水释磷,而后吸附直至达到平衡;随着上覆水初始磷浓度的升高,当基质中的磷含量低于上覆水中的磷浓度时,则从水体吸磷直至达到平衡.将不同环境因子相比较,上覆水为碱性条件(pH=11.3)时基质的释磷量最大,厌氧条件次之,上覆水的pH值增加和氧化还原电位降低是湿地基质释磷的主要机制.     

反硝化聚磷菌富集条件的研究

采用SBR反应器,通过厌氧/好氧、厌氧/缺氧两个阶段的驯化培养来富集反硝化聚磷菌(DPBs),考察了不同条件对DPBs富集情况的影响。在培养驯化过程中应抑制厌氧/好氧阶段聚糖菌的生长以及厌氧/缺氧阶段反硝化菌的繁殖。结果表明,乙酸是DPBs生长的优良碳源;在pH=8.5的条件下,按C/P值为8进水、按N/P值为4在缺氧段添加硝酸钠进行培养驯化可富集大量的DPBs。     

Phosphorus release-storage reaction and organic substrate behavior in biological phosphorus removal

This paper represents the results of an experimental investigation conducted on the mechanism of biological phosphorus removal. The relationship between phosphorus release-storage reaction, and behavior of extracellular and intracellular organic substrates under anaerobic-aerobic conditions is studied in detail.The results obtained are as follows: (1) the amount of intracellular carbohydrate increases under the presence of extracellular glucose, but decreases when extracellular glucose is depleted in the anaerobic condition. (2) The amount of intracellular poly-β-hydroxybutylate (PHB) gradually increases under the anaerobic condition. The increase in intracellular PHB content appears to be related to the decrease in intracellular carbohydrate content when extracellular glucose is depleted. (3) Rate of phosphorus release under the anaerobic condition is related to the amount of releasable phosphorus in the cells. The observed ratios of postulated “maximum phosphorus storage capacity” to total amount of intracellular phosphorus are similar to those of the low molecular weight polyphosphate fraction in the cells. (4) Release of phosphorus under the anaerobic condition appears to be related to both ingestion of extracellular organic substrates and formation of intracellular PHB. (5) Release of phosphorus under the anaerobic condition appears to be limited once a fixed portion of intracellular phosphorus is released, even if substantial amount of extracellular organic substrate still remains available. (6) The amount of intracellular PHB increases in the subsequent aerobic condition under presence of a sufficient amount of extracellular organic substrate, but the amount decreases when the extracellular organic substrate is depleted. Similarly, the amount of intracellular carbohydrate initially increases, then gradually decreases following the decrease in PHB content. (7) Ingestion rate for phosphorus in the aerobic condition appears to be dependent on unsaturated storage capacity of intracellular phosphorus as well as on the concentration of extracellular phosphorus.     

Biological phosphate removal by activated sludge under defined conditions

A simple, one reactor vessel system, called a fill-and-draw system, was developed for the study of enhanced biological phosphate removal under defined conditions. Sludge was grown in a medium with acetate and glucose as sole energy and carbon sources. The sludge was exposed to cycles with three distinct, consecutive periods; first an anaerobic period, then an aerobic period and finally a settlement period. In the period of settlement one third of the liquid was replaced with fresh medium. Sludge grown under this regime became considerably enriched with polyphosphate-accumulating bacteria. The polyphosphate content reached up to 110 mg P/g dry weight. The amount of polyphosphate in the cells during steady state depended on the acetate:glucose ratio, the nitrate and phosphate concentration in the medium. Highest phosphate accumulation was obtained with an acetate:glucose ratio of 9:1. Intracellular polyphosphate was formed during the aerobic period and was anaerobically hydrolysed and released as phosphate into the medium. In the absence of oxygen and in the presence of 2g acetate-COD/l, 80–90% of phosphate was released by sludge containing 100 mg P/g dry weight. In the absence of acetate only 2–19% of the accumulated phosphate was excreted.     

Endogenous metabolism of Candidatus Accumulibacter phosphatis under various starvation conditions

The endogenous processes of Candidatus Accumulibacter phosphatis (referred to as Accumulibacter), a known polyphosphate-accumulating organism (PAO) responsible for enhanced biological phosphorus removal systems (EBPR), were characterized during 8-day starvation under anaerobic, anoxic, aerobic and intermittent aerobic–anaerobic conditions. A lab-scale EBPR culture with Accumulibacter representing over 85% of the entire bacterial population as quantified with fluorescence in-situ hybridization was used in the study. Cell decay rates were found to be negligible under anaerobic and anoxic conditions and may be ignored in activated sludge models. The decay rate under aerobic conditions was determined to be 0.03/d at 22 °C, considerably lower than the values commonly used in activated sludge modeling. Polyphosphate and glycogen were utilized simultaneously under anaerobic and anoxic conditions for maintenance energy production, with glycogen being the primary energy source until the glycogen content reached very low levels. Glycogen was used by Accumulibacter as the primary source of energy for maintenance under aerobic conditions in the absence of polyhydroxyalkanoates. However, Accumulibacter did not seem to use polyphosphate for energy production during aerobic starvation, clearly contrasting the anaerobic and particularly the anoxic case. Intermittent aerobic–anaerobic storage resulted in not only negligible cell decay rate, but also slower rates of glycogen and polyphosphate utilization, and may therefore be an effective strategy for long-term storage of EBPR sludge.     

序批式生物膜法除磷机理研究

利用^31P-核磁共振谱图证实了生物除磷的机理，即除磷菌在厌氧条件下分解胞内的聚磷酸盐并释放出正磷酸盐形式的无机磷酸盐，而在好氧或缺氧条件下吸收胞外的无机磷酸盐后转化为聚磷酸盐而贮存于胞内。同时证明了淹没序批式生物膜反应器中磷的去除是由生物完成的。     

Could polyphosphate-accumulating organisms (PAOs) be glycogen-accumulating organisms (GAOs)?

Polyphosphate (poly-P) is known to be a key compound in the metabolism of polyphosphate-accumulating organisms (PAOs). In this study, a sludge highly enriched (80%) in Candidatus Accumulibacter phosphatis (hereafter referred to as Accumulibacter), a widely known PAO, was used to study the ability of these microorganisms to utilize acetate anaerobically under poly-P-limiting conditions. The biomass was subject to several anaerobic and aerobic cycles, during which the poly-P pool of PAOs was gradually emptied by supplying feed deficient in phosphate and washing the biomass at the end of each anaerobic period using media containing no phosphorus. After three cycles, phosphorus was hardly released but PAOs were still able to take up acetate and stored it as polyhydroxyalkanoates (PHA), as demonstrated by post-FISH chemical staining. Glycogen degradation increased substantially, suggesting PAOs were using glycogen as the main energy source. This is a key feature of glycogen-accumulating organisms (GAOs), which are known to compete with PAOs in enhanced biological phosphorus removal (EBPR) systems. The ratios between acetate uptake, polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV) production, and glycogen consumption agree well with the anaerobic models previously proposed for GAOs.     

Foam Formation, Anaerobiosis and Microthrix Parvicella

Microscopic examinations of the sludges associated with two incidents of foam formation in anaerobic digesters are described. In both cases, the dominant filamentous species was Microthrix parvicella. Preliminary growth studies with this species indicated that it could grow in both aerobic and anaerobic environments, but that in an anaerobic regime it did not produce polyphosphate granules. This suggests that M. parvicella may be involved in the luxury uptake of phosphate and, under strict anaerobic conditions, could compete with acetoclastic methanogens for acetate.     

Luxury uptake of phosphorus by sediment bacteria

This note reports the results of experiments aimed at confirming the luxury uptake of phosphorus (P) by sediment bacteria as polyphosphate (Poly-P). Aerobic suspensions of sediments from two different sites were spiked with 1 mg P/L as orthophosphate and augmented with acetate (a fermentation product) or glucose. The orthophosphate was rapidly taken up over a period of a few hours. When these aerobic uptake experiments were made anaerobic and additional organic carbon added, only the acetate-amended sediment released a significant amount of the added phosphorus. It was hypothesised that during the aerobic stage, and with the addition of acetate, some of the phosphorus was accumulated as Poly-P by sediment microorganisms, which was released during the subsequent anaerobic stage (provided acetate was still present). Two lines of evidence--transmission electron microscope analysis of sediment bacteria and 31P-NMR analysis of sediment extracts--are presented to support the hypothesis that a portion of the phosphorus taken up during the aerobic experiments was stored as Poly-P.     

Biochemical model for enhanced biological phosphorus removal

Enhanced biological phosphorus (bio-P) removal from wastewater is a promising technology for which the fundamental mechanisms are still unclear. The purpose of this paper is to present a biochemical model that explains bio-P removal mechanisms occurring under anaerobic, aerobic and anoxic conditions of the process. A bio-P bacterium is referred to as one that can store both polyphosphate and carbon (as poly-β-hydroxybutyrate for example). In this communication, observations from the literature are first reviewed and mechanisms of bacterial bioenergetics and membrane transport are summarized. The model for bio-P metabolism under anaerobic, aerobic and anoxic conditions is then presented. The role of polyphosphate under anaerobic conditions is suggested to be as a source of energy both for the reestablishment of the proton motive force, which would be consumed by substrate transport and for substrate storage. The role of the anaerobic zone is to maximize the storage of organic substrates in bio-P bacteria. For this purpose the supply of readily available substrates should be maximized and the presence of electron acceptors (molecular oxygen or oxidized nitrogen) minimized. Under subsequent aerobic or anoxic conditions, bio-P bacteria will accumulate polyphosphates in response to the availability of electron acceptors (oxygen or oxidized nitrogen) for energy production. Carbon reserves in bio-P bacteria should provide energy for growth and for soluble phosphate accumulation as polyphosphate reserves.     

Endogenous processes during long-term starvation in activated sludge performing enhanced biological phosphorus removal

In many biological wastewater treatment systems, bacterial growth and the amount of active biomass are limited by the availability of substrate. Under these low growth conditions, endogenous processes have a significant influence on the amount of active biomass and therefore, the overall system performance. In enhanced biological phosphorus removal (EBPR) systems endogenous processes can also influence the levels of the internal storage compounds of the polyphosphate accumulating organisms (PAO), directly affecting phosphorus removal performance. The purpose of this study was to evaluate the significance of different endogenous processes that occur during the long-term starvation of EBPR sludge under aerobic and anaerobic conditions. Activated sludge obtained from a laboratory sequencing batch reactor was used to perform a series of batch starvation experiments. Under aerobic starvation conditions we observed a significant decay of PAO (first-order decay rate of 0.15/d) together with a rapid utilization of polyhydroxyalkanoates (PHA) and a slower utilization of glycogen and polyphosphate to generate maintenance energy. On the other hand, anaerobic starvation was best described by maintenance processes that rapidly reduce the levels of polyphosphate and glycogen under starvation conditions while no significant decay of PAO was observed. The endogenous utilization of glycogen for maintenance purposes is currently not included in available EBPR models. Our experimental results suggest that mathematical models for in EBPR should differentiate between aerobic and anaerobic endogenous processes, as they influence active biomass and storage products differently.     

The storage of acetate under anoxic conditions.

Till now the role of storage in activated sludge processes under transient conditions has been deeply investigated under anaerobic (EBPR processes) or aerobic (bulking control) environments. Little attention has been given to the role of storage in processes including anoxic environments. Hence, the aim of the present work was to investigate the anoxic storage along with other substrate removal mechanisms under transient conditions. Several mixed culture were ad hoc selected under anoxic environment and periodic feeding (acetate as carbon source) at different organic load rate (OLR) and feed length; then their transient response to substrate spike was investigated by batch tests under both anoxic and aerobic conditions. The relative role of different mechanisms in the substrate removal was established on the basis of COD balance assuming that the acetate COD removed from the liquid phase could be oxidised for energy needs or recovered into solids as poly-3-hydroxybutyric acid (PHB) (storage), other internal precursors or intermediates (accumulation) and active biomass (growth, as estimated by ammonium uptake). In all tested conditions, growth response was very little while PHB storage was prevailing. In some operating conditions, indirect evidence of accumulation (in forms still to be identified) was also found. The transient response was not affected by the presence of free amino acids, at least for the unacclimated mixed culture under observation. Transient response under aerobic condition was quite similar to the anoxic one.